This invention relates to apparatus for detecting in a body inserts, thickness unevenness or impurities such as air, metal or the like which have different radiant ray absorption coefficiencies from that of matrix material. All such discontinuities are for convenience herein referred to as inserts.
In prior radiography for detecting inserts, impurities or thickness unevenness of molding, welding or sheet, there are provided a radiant ray source placed facing the object to be inspected and an X-ray film arranged along the object opposite to the radiant ray source for detecting X-ray distribution which is projected there by way of the object. This method requires developing process of the film which requires much time, and further requires much film and is expensive for wide area inspection. Therefore, it cannot be availed to the inspection of sheet on line of a plant.